Local rumour is that VLM are to start up a route to BRU and possibly LCY.
I'm not sure that there has ever been a direct ABZ/BRU service.
ABZ/LCY has been tried with varying degrees of success by Air UK / KLM UK / British European / Scot Airways in the past few years but there is currently no service.
BTW, ABZ can handle the B737 easily, e.g. non-stop charter B737-800 to Cyprus (~4.5 hours) has been running for the past few years. B767-200/300 is a fairly regular visitor and and even A330 have landed there before now!